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Best method of autoguiding EQ3 pro without computer?


Welrod50
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All,

I have decided that 1 minute subs with the EQ3 Pro are just not cutting the mustard and have elected to move into auto guiding. Now, I am after 3 or 4 minute subs (don't need any more to be fair) and also wish to keep the equipment down, so am not overly interested in using a computer and conventional guide set up. I realise this limits my options, but set up time and carrying to and fro is time consuming and complicated enough, without adding to it ;)

I have therefore leaned towards the SW synguider / Celestron Neximage guiders and so my question really is this.....

OAG or 50mm guidescope??

Now, I am going to the astro exhibition in Warwickshire on Saturday and hope to find some good answers there, but I am also highly impatient hence my question here to the enlightened masses :)

I read that the synguider will not focus when used with a 50mm guidescope and also that off axis guider creates all sorts of headaches when trying to focus the guide cam and DSLR.

Does anyone have any sound advice they could share and any recommendations for a solid, straightforward guide system which will work??

All input very gratefully received :)

Clear skies.....

Scott.

ps, roll on Saturday!!

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Hi, Scott,

sorry, I have never used the integrated guide cameras, so can't help you on your hoice of the Celestron or SW variant. But I woudl guess the SW would be most compatible.

However, I have used both OAG and separate guidescopes and both methods have issues.

If you went to an OAG, the guide camera will be trying to share the space with your main camera. They will be quite close together and looking at the SW Synguider, it is a bit chunky. I guess you would be imaging with a DSLR, so I wonder if they will all play nice together? This also adds some weight to the focuser, so that might also need tightening to keep it straight.

The guidescope method also has some issues. It is important they all look at the same point in space and that they are VERY securely held together. You will need to account for the additional weight trying to unbalance the mount.

So. lots of words, possibly not so helpful. What I woudl really suggest you do is take your DSLR with you and try it on an OAG. If it fits and there is room to focus, then looks like you have a choice. If it doesn't fit, then you only need to sort out the guidescope option.

Good luck and I hope you enjoy Saturday.

Gordon

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What sort of focal lengths are you imaging at?

I can get decent 4 min subs at 200mm with reasonable polar alignment and balancing on my EQ3-Pro...

I used a Synguider with mine but had one of the very early EQ3-Pros which had guideport issues which were eventually sorted by a couple of firmware upgrades that required a new motor controller....

I can't say that I was that impressed with the Synguider used as a finder guider not enough choice of guidestars but it worked very well on the Skywatcher ST80..

I never got round to trying it on an OAG, Perhaps somebody has tried it and can advise on its suitabillity...

Peter...

Sent from my GT-P7300 using Tapatalk HD

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I am a recent 'convert' to off axis guiders (OAGs) but would urge you not to use one with a SynGuider as this device really could do with the brightest possible star to work on and an OAG would not be the best choice here. Add in the complication of achieving focus with the SynGuider when you only have a dim screen to work with and you are setting yourself up for a load of grief.

I really think that if you need to keep the weight down (likely as this is an EQ3) then an OAG or 50mm finder/guider with a normal autoguiding camera, laptop and guide software would be much less hassle.

The SynGuider certainly works - I have reviewed one and it was pretty good BUT I used it with an 80mm guidescope on an EQ6.

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Thanks guys for the input.

OK, I'm imaging at 650mm prime focus on the 130 PDS. The EQ3 Pro I bought middle of last year so should be pretty new as regards firmware, although I am yet to try the guideport of course. The ST4 input is in the hand controller and not fitted intot he mount. The focuser on the 130 is a pretty solid dual speed affair and the camera weighs 1kg. I have rigged it up before now to image through an EP, parfocally attached and racked right out to achieve focus. Even with all that lot hanging off it, it was solid.

Having recently gone to town collimating the polar scope and recollimating the OTA, I can comfortably get 1 minute subs with no trailing at all with a good polar alignment. I have tried 1.5 minutes and these do exhibit a bit of trailing - not a lot, but enough for me to discard them as I want them to be spot on. I think if I used the camera straight onto the mount with my spare dovetail bar I would get 3 minutes + at 150mm focal length (lens). I shy away from this though as my lens is pretty sharp and stopped down to f5 gets sharper still, but it then is nowhere near as good as the OTA at prime focus for sharpness, and imaging time is precious, so I aim for maximum success with minimal experimenting each time.

I have to say that, having read up some more since this original post, i am moving away from OAG and also from using synguider with small miniguider as I am not convinced either will work overly well. My OTA with DSLR attched weighs a tad under 5kg assembled. I have adjusted the slew speed down on the mount and although I believe I'm pretty much on the limit for imaging, do think I could get away with another kilogram if I kept the guidescope small.

I am therefore considering one of the following two options:

1. 60 - 70mm refractor, circa 400mm focal length, with synguider and no computer.

2. Orion (or similar) miniguider package running through a netbook or small laptop.

I didn't want the extra hassle of computer/cables/power issues and so on, but am now thinking that if I am going to do it, I need to do it properly.

I've waffled a bit, but at least everyone knows what's what.

Any thoughts peeps??

:)

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Hi Scott

I agree totally about the PC issue. I ended up making an analogue guider - basically a little 7" LCD TV relaying the guide cam image and 4 optic fibres and photodiodes to detect when the star image moves on the screen up/down, left/right. Sounds potty but it works better than I ever imagined. Happy to send you the details if you want.

I think you are right about the OAG - I have one and still haven't managed to successfully get the two optical paths right.

On the guide scope, you might look at the 50mm skywatcher finder. You can get an adapter (Modern Astronomy) for it that screws in the end and converts it for T thread - but a few tubes from the junkbox and judicious use of jubilee clips would work as well and be cheaper. FL is about 150mm, and a barlow would extend that (and fix any backfocus problems).

The great thing about a guidescope is it doesn't actually have to point at what you are imaging to guide. 400mm sounds a bit long to image at 150 - dimmer image, longer guide exposures, smaller fov, no suitable guide star etc etc. You might end up putting a focal reducer on the guidescope.

Simon

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